Ervin, Stephen

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Aquatic Commons

8 NOTICIAS DE GALAPAGOS No. 48 
THE NESTING OF THE DARK-BILLED CUCKOO IN THE 
GALAPAGOS 
By: Stephen Ervin 
reported to be 
abundant in and 
following EI Nifio-
Southern Oscillation 
(ENSO) years with 
high rainfall. 
Jackson (1985) 
The Dark-billed 
Cuckoo (Coccyzus 
melacoryphus), like 
other members of the 
genus, has the 
reputation of being 
secretive in its daily 
activities and in its 
breeding habits. 
Harris (1982) noted 
that in the Galapagos 
the species is "More 
often heard than 
seen." Gifford 
(1919) reported the Dade-billed Cuckoo (Aguatero). 
reported that the 
cuckoo became 
much more abundant 
during the 1982-83 
ENSO. Workers at 
the Charles Darwin 
Research Station and 
local residents ofIsla 
birds to be "shy" and, although they have been 
reported on most of the Islands in the Archipelago, 
there was "seldom more than one individual being 
seen at a time." Consequently, there have been few 
reports of nesting behavior. Gifford (1919) reported 
that nests were "not infrequent," but he described 
only one active nest. Swarth (1931) compared the 
morphology of mainland and Galapagos forms and 
did not comment on reproductive behavior. Many 
longtime Galapagos residents and visiting scientists 
have never seen the nest of the cuckoo. 
Related species in the genus, the Yellow-billed 
Cuckoo (C. americanus) and the Black-billed Cuckoo 
(c. erythropthalmus), have long breeding seasons, 
abbreviated incubation periods, staggered incubation, 
asynchronous hatching, and very early nest departure 
of the young (Spencer 1943, Hamilton and Hamilton 
1965). Hamilton and Hamilton (1965) suggested 
that these adaptations are correlated with seasonally 
abundant food supplies and insure survival of at least 
a part of the brood. Early maturity is also suggested 
to be a mechanism to permit rapid independence of 
young in food gathering. Such adaptations occur in 
widely fluctuating environments where food supplies 
vary considerably from year to year. Rainfall in the 
Galapagos fluctuates greatly from year to year. In the 
Galapagos, the Dark-billed Cuckoo is commonly 
Santa Cruz also indicated that the cuckoo population 
increased in other wet years including the year of my 
visit, 1987. The local name for the cuckoo, 
"Aguatero," reflects this association. Cuckoos are 
known to breed on dry islands following an ENSO 
(Curry and Stoleson 1988). 
During the spring of 1987, I was able to locate four 
nests of the Dark-billed Cuckoo in the dry zone 
vegetation in the vicinity of the Darwin Station east 
of the town of Puerto Ayora on Academy Bay, Isla 
Santa Cruz. The vegetation was dominated by a 
variety of small trees and shrubs and the cacti 
Jasminocereus thouarsii and Opuntia echios. 
The first evidence of breeding of the cuckoo in 
1987 came on 2 February with the discovery of a pair 
of adults feeding a single young in the scrub vegetation 
at the Darwin Station. The young bird was barely 
capable of flight and was not full y feathered. It could 
not be captured because of the ease with which it fled 
through the scrub of salt bush (Cryptocarpus 
pyriformis) and espino (Scutia pauciflora). 
Considering my experience at later nests, I would 
estimate the fledgling's age at approximately 10 to 
12 days. Subtracting this and a minimum incubation 
period of approximately 11 days would establish a 
date for the first egg of 10-12 January. December 
1986 had a total rainfall of 12.4 mm while January 
December 1989 NOTICIAS DE GALAPAGOS 9 
1987 had a total of 124.7 mm. Theonsetofbreeding 
corresponds to the onset of the rainy season. 
Nest #1 was located on 6 February in an acacia 
(Acacia sp.) approximately 3 m from the ground. 
The nest was not readily accessible for measurements 
of eggs or chicks. The nest was similar to that 
described for the Black-billed Cuckoo by Spencer 
(1943) with the exception of the absence of pine 
needles. The nest was composed of small sticks and 
twigs with an outside diameter of approximately 8-
10 cm and a cup diameter of 5-6 cm. The nest 
contained four bluish white, chalky eggs. The adult 
flushed from the nest at my approach and returned 
immediately after I moved a short distance away 
from the nest. By 0815 on 8 February two eggs had 
hatched and a third had pipped. The brooding adult 
left at my approach. The young closely resembled 
those of the Yellow-billed and Black -billed Cuckoos 
in appearance and behavior (Spencer 1943, Hamilton 
and Hamilton 1965), but no buzzing sound was given 
by the chicks as reported in those two species. The 
young could be induced to beg by shaking the nest 
branch. By 9 February at 1230, three young were 
present and one egg remained unhatched. The young 
birds could no longer be induced to beg. By 1100 on 
14 February the nest contained a large chick, and a 
smaller chick was perched bittern-like on a branch 
near the nest. There was no sign of the third chick or 
the unhatched egg. The pose of the chick out of the 
nest was identical to the pose described by Bent 
(1940) for the Black-billed Cuckoo. 
Nest #2 was located on 26 February in an acacia 
next to a pad of opuntia (Opuntia echios) that intruded 
into the canopy. The nest was 2.5 m above the 
ground. The adult was incubating five eggs. 
Measurements of the eggs were: 2.85 by 2.30 cm, 8.5 
g; 2.80 by 2.25 cm, 8.0 g; 2.80 by 2.30 cm, 8.0 g; 3.10 
by 2.45 em, 10.5 g; and 3.00 by 2.50, 10.5 g. Incubation 
continued until 6 March when one egg had hatched 
by 0845. By 1050, three eggs had hatched and 
surprisingly a sixth egg was present. Two of the 
chicks weighed 8.5 and 9.0 g. Since the nest was 
checked only by touch in the interval between 26 
February and 6 March, I cannot be sure of the date of 
the laying of the sixth egg, but it was after 27 
February. By 0720 on 7 March there were four young 
and two unhatched eggs. I assumed the fourth egg 
Table 1. Dark-billed Cuckoo nestling weights in 
grams for Nest #2, Isla Santa Cruz. 
Chick # 03/08 
002 23.5 
003 20.5 
004 16.5 
005 21.0 
006 13.0 
Dates: 
03/09 03/10 
25.5 32.0 
24.0 27.0 
21.0 2q.0 
23.5 27.5 
16.5 
03/11 
27.5 
29.0 
32.5 
hatched in the afternoon of the previous day. The 
fifth egg hatched by 1250 (the chick was eventually 
marked as #006). On 8 March the eyes had opened 
on the third-day chicks (#s 002 through (05) and I 
noted a wide discrepancy in the size of the chicks. 
The chicks were weighed and marked with colored 
leg bands as well as the numbered bands noted above. 
The chicks' legs were already sufficiently developed 
and adult size (#2) leg bands were attached without 
risk ofloss. Weights on this and subsequent dates are 
noted in Table 1. 
On 10 March the smallest chick (#006) was missing 
from the nest and on 11 March a second chick (#003) 
had disappeared. When handled, the chicks defecated 
a sticky brown liquid of digested hawkmoth larvae. 
By 11 March, Chick #002 was sitting on a branch 
adjacent to the nest and was more active, possibly 
accounting for the small weight loss. The same 
bittern-like posture seen at Nest #1 was again 
observed. On 12March,Chick#OO5wasfounddead 
beneath the nest and was preserved for the Station's 
collection. One chick (#004) remained in the nest. 
On 13 March the sixth egg hatched by 1415. Noneof 
the older chicks were present. The new chick was 
begging, but apparently was not fed or brooded as it 
was found dead in the nest by the morning of 14 
March. This chick was never banded. It is also 
preserved at the Station. Unfortunately none of the 
marked chicks were observed during the remainder 
of my stay; they apparently dispersed rapidly from 
the nest site into the scrub. 
Nest #3 was located on 10 March in a lantana 
(LantanapeduncuJaris) overlain by climbing passion 
flower vines (Passiflora foetida). The height was 
approximately 2.5 m. This nest was not covered by 
10 NOTICIAS DE GALAPAGOS No. 48 
a canopy of vegetation as were the previous two 
nests. The nest contained four eggs and by 1115 on 
12 March a fifth was present. I was not able to return 
to this nest until 24 March when one approximately 
4-5 day old chick and two eggs remained. If one egg 
per day was laid as usual and the chick was from the 
first egg laid (8 March) the incubation time was 11-
12 days. The chick was banded and weighed (25.0 g) 
on 26 March. There was no sign of broken eggs 
beneath the nest. The chick and remaining eggs had 
disappeared by the end of March. 
Nest #4 was located in a white mangrove 
(Laguncularia racemosa) on 24 March. The adult 
present was incubating two eggs; the other adult was 
bringing small sticks and lichen to the nest. The nest 
was 3.5 m from the ground. By 0830 on 2 April the 
nest contained three eggs. Between 6 and 9 April no 
incubation was observed, and no birds were present 
near the nest. Following heavy rains (22.8 mm) on 9 
April the nest was found tilted and abandoned with 
one cracked egg present. 
In its breeding biology, the Dark-billed Cuckoo of 
the Galapagos acts like the other members of the 
genus. It has a short incubation period and 
asynchronous hatching with considerable variability 
in chick size. Chicks grow rapidily and are able to 
move about in the vegetation before they are capable 
of flight. The capability of feeding themselves at an 
early age is conjectural although ample supplies of 
larvae of the hawkmoth were evident in the area. The 
existence of second nestings in the same season is 
not known. It is quite likely that populations of this 
cuckoo fluctuate greatly in number, and the apparent 
paucity of birds in dry years does not necessarily 
reflect movement to other habitats. 
ACKNOWLEDGMENTS 
I thank the staffs at the Charles Darwin Research 
Station and Galapagos National Park for their 
assistance during my stay, particularly Gayle Davis 
Merlin for the rainfall data and Cirilo Barrera and 
Alberto Jaramillo for their help in locating Nests #1 
and #3. My colleague Dr. Wallace Harmon was 
kind enough to review the manuscript. 
LITERATURE CITED 
Bent, A.C. 1940. Life histories of North American 
cuckoos, goatsuckers, hummingbirds and their 
allies. U.S. National Museum Bulletin 176. 506 
pp. 
Curry, R.L., and S.H. Stoleson. 1988. New bird 
records from the Galapagos associated with the El 
Nino-Southern Oscillation. The Condor 90:505-
507. 
Gifford, E.\V. 1919. Field notes on the land birds of 
the Galapagos Islands and of Cocos Island, Costa 
Rica. Proceedings of the California Academy of 
Sciences, Fourth Series 2:189-258. 
Hamilton, W.J., andM.E. Hamilton. 1965. Breeding 
characteristics of Yellow-billed Cuckoos in 
Arizona. Proceedings of the California Academy 
of Sciences, Fourth Series 32:405-432. 
Harris, M. 1982. A field guide to birds of the 
Galapagos. Revised edition. Collins, London. 
Jackson, M.H. 1985. Galapagos. A natural history 
guide. University of Calgary Press, Calgary, 
Alberta, Canada. 
Spencer,O.R. 1943. Nesting habits of the Black-
billed Cuckoo. Wilson Bulletin 55: 11-22. 
Swarth, H.S. 1931. The avifauna of the Galapagos 
Islands. Occasional Papers of the California 
Academy of Sciences 18:1-299. 
Stephen Ervin, Department of Biology ,California 
State University, Fresno, California 93740, USA. 


The nesting of the Dark-billed Cuckoo in the Galapagos

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The nesting of the Dark-billed Cuckoo in the Galapagos

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